Questions tagged [orbital-elements]

Questions about the parameters needed to specify the characteristics of an orbit.

Filter by
Sorted by
Tagged with
70
votes
4answers
9k views

How does the Earth move in the sky as seen from the Moon?

I just want to be sure I am visualizing this correctly, because it seems odd. The Moon is tidally locked to the Earth but there are wobbles to its motion due to libration. So from a point on the ...
16
votes
3answers
3k views

What are "non-Keplerian" orbits? What are some familiar examples in our solar system, and can some still be closed?

This excellent answer to Forms of stellar orbits around the galactic center invokes the following concepts: non-Keplerian orbits closed orbits I have a fairly good idea what these mean and so might ...
14
votes
1answer
431 views

Orbital velocity of a planet - why is my calculation off by about 10%?

I am not sure if I am doing something wrong, or misunderstanding Reider and Kenworthy (2016). I'm just trying to reproduce the orbital velocities listed in Table 1. The second paragraph of Section II ...
10
votes
2answers
2k views

What is the difference between the two terms named "Eccentricity" and "Ellipticity"?

I don't get the difference between the two terms named "Eccentricity" and "Ellipticity", especially, in astronomy. I understand eccentricity as a measure of the curvature of a ...
9
votes
3answers
351 views

Asteroids conjunction

I am currently writing a C++ program to show asteroids in 3D, and find close approaches or collisions. I got my orbital elements from JPL https://ssd.jpl.nasa.gov/sbdb_query.cgi. So far so good, with ...
8
votes
1answer
971 views

Could Planet X have a perihelion much closer than 300 AU and still be responsible for the gravitational interaction with 19 TNOs?

In August, Michael Brown and Konstantin Batigyn proposed new data concerning the hypothetical Planet X to explain the orbits of the 19 TNOs. They suggest a perihelion of 300 AU, but might Planet X be ...
8
votes
1answer
753 views

What is Charon's ascending node in reference to?

NASA's orbital elements given for Charon's orbit are given at https://ssd.jpl.nasa.gov/?sat_elem. The ascending node is defined as being "measured from the node of the reference plane on the ICRF ...
8
votes
2answers
147 views

If the hypothesized planet behind the Kuiper belt existed, would it have a barycenter outside the Sun?

In 2016, an additional object rotating our Sun has been suggested. Assuming it has 5 Earth masses, would the planet or black hole proposed by Brown and Batigyn have a barycenter within the Sun or ...
8
votes
1answer
365 views

Why is Neptune true anomaly decreasing?

So I've been having fun with trying to determine where the perihelia of different planets are (using JPL Horizons). And by the time I got to Saturn, something weird started happening. I've noticed ...
7
votes
2answers
861 views

How do I calculate the positions of objects in orbit?

In a model of the solar system, given the Sun is at the point $(0, 0, 0)$, an given the six orbital elements for each object in orbit ($a$, $\epsilon$, $i$, $\Omega$, $\omega$, $M_0$), how can I ...
7
votes
1answer
266 views

Orbital eccentricity variation of the other planets?

On Earth, it's fairly well published, mostly in climate change related articles, that the Earth's orbital eccentricity operates on a 413,000 year cycle with roughly 90,000–125,000 year variation ...
7
votes
1answer
251 views

Saturn's tropical year?

What is the value of Saturn's "tropical year" (as opposed to its "sidereal year"). I am seeing it listed as 10 days shorter (10,747 days) than the sidereal year (10,759.22 days). How could this be ...
6
votes
3answers
994 views

"Periapsis" or "Periastron"?

I was taught from Bate Mueller and White, that the proper terms for the closest and furthest points and distances from a body in orbit around another unspecified body are "periapsis" and &...
6
votes
1answer
438 views

Forms of stellar orbits around the galactic center

Do all stars in orbit around Sagittarius A have approximately circular orbits or are there stars that orbit the Milky Way center very elliptically, like being in the Milky Way's outer rim at apoapsis ...
6
votes
1answer
167 views

Kepler's equation and eccentric anomaly

From the wiki article about eccentric anomaly follows: $$\cos E = \frac{x}{a}$$ $$\sin E = \frac{y}{b}$$ where E - eccentric anomaly, a - semi-major axis, b - semi-minor axis, P = P(x,y) a point on ...
6
votes
1answer
380 views

Cannot identify mistake in calculating orbital eccentricity vector; magnitude equals one instead of zero (with python code)

I have a gravitational nbody simulation, for which I would like to determine various orbital parameters. For each body, I have 3-D vectors (x,y,z -space) for position, velocity, and acceleration. I am ...
6
votes
2answers
263 views

Clearing the Neighbourhood: Definition of 'Orbital Region'?

I am trying to determine how wide a 'neighbourhood' a planet is expected to clear. However, the Wikipedia article on the matter provides no clarity, simply stating that a planet is expected to clear ...
5
votes
1answer
416 views

Confused on how you are supposed to calculate eccentricity without apsides

I'm kinda confused on how to calculate either the apsides or the eccentricity without knowing one or the other. Let's say you have an object in orbit around another. If you know the current distance, ...
5
votes
4answers
600 views

Inclination in Kepler's laws

So, you can determine the location of an object in an orbit at any given time via Kepler's laws, but how do you determine the orbital inclination at any given point in time?
5
votes
2answers
336 views

Keplerian Elements for Approximate Positions of the Major Planets

Simple question here. I am working on something that needs to compute an orbital path using Keplerian Elements. When doing some research I came across this JPL page: Click Here. Within that link is a ...
5
votes
3answers
180 views

Kepler's Law, focal points - Heliocentric or Barycentric?

It is known that all the mass in the Solar system moves around the Barycenter. For the two focal points in Kepler's law; is the first focal point $F_1$ a Heliocenter? Or is it actually a Barycenter? ...
5
votes
1answer
174 views

Is there a preference for orbital planes of planetary systems to be aligned with the galactic disk?

I'm not sure for how many planetary systems we have a fairly good idea of the inclination and "argument of periapsis" of the orbital plane. I'm assuming there are a number of them that we can estimate ...
5
votes
1answer
172 views

How many observations does it take to determine the orbit of a TNO

Several observations of a distant solar object must be taken before determining its orbit, but in the case of objects discovered beyond Neptune's orbit, just how many are required over what period of ...
5
votes
1answer
999 views

Simulate an orbit with orbital elements

I want to simulate the orbits of the planets from our solar system. I want to use orbital elements to calculate the current position(xyz) at a time t. The simulation doesn't have to be too exact, but ...
5
votes
1answer
1k views

Why would the Earth's solar analemma would be still a figue eight even if Earth's orbit was circular?

The Earth's solar analemma is a diagram showing the deviation of the Sun from its mean motion in the sky, as viewed from a fixed location on the Earth. ... For [a planet] with a circular orbit but ...
5
votes
0answers
64 views

Are occultation observations used/useful for orbit determination?

The IAU Minor Planet Center lists $(486958)\space 2014 \space MU_{69}$ "Ultima Thule" as having an uncertainty parameter of 2, based on the observation arc of 851 days, from its discovery in 2014, to ...
4
votes
4answers
6k views

Can one approximate the semi-major axis of an orbit as the average orbital distance for eccentric orbits?

Kepler's 3rd Law (regarding the relation between orbital period and the semi-major axis of an orbit) applies to all elliptical orbits. But as I understand it, the only reason it is safe to use the ...
4
votes
1answer
417 views

Orbits using Newtons laws

I am making a small orbit simulator. I figured out Kepler's laws and know how to work with them to "update" an orbit based on time. So now I want to know how I can describe orbits with newton laws. ...
4
votes
1answer
364 views

Can a binary star optically "orbit" a planet?

I was watching a science fiction anime from the mid 70's. In it, there was a star orbiting a planet. Since this seemed impossible, and I had never heard of it, I looked on the internet to see if this ...
4
votes
1answer
236 views

Calculating obital velocity from radial velocity

I'm not really a physicist so I don't know if it's possible to get the real orbital velocity of a star from its radial velocity. I'm working on a paper for school and I want to get the mean velocity ...
4
votes
1answer
230 views

Converting orbital elements from equatorial reference frame to ecliptic

I have a bunch of orbital elements (inclination, longitude of the ascending node, mean anomaly, argument of periapsis) that are all referenced from an equatorial reference frame. But the program I am ...
4
votes
1answer
913 views

How would one calculate the synodic period between 3 planets?

I don't know if this is the correct term, but how would one calculate the time it takes for 3 planets to lie on the same line?
4
votes
2answers
524 views

Sun's orbital elements

I have the orbital elements of an asteroid's heliocentric motion (the orbit has non-zero inclination and is elliptical). But I want to simulate the motion of the sun around the asteroid. So without ...
4
votes
1answer
65 views

Have we indirectly measured GW driven orbital decay in anything besides binary pulsars?

Binary systems decay for all sorts of reasons. I'm asking specifically about orbital decay due to gravitational wave emission. All of direct GW detections of binary systems have come with orbit ...
4
votes
0answers
35 views

Has the inclination of the orbital plane of Phobos and Deimos followed that of Mars' axial tilt?

Phobos and Deimos are very close to Mars' equatorial plane (the inclination of their orbits is roughly 1°). The axial tilt of Mars has changed a lot over time, and might have had a inclination of over ...
3
votes
3answers
198 views

Why is it impossible to estimate the inclination of an exoplanet with the Radial Velocity Method?

The formula of the radial velocity is: $$v_i= V - K(\sin(f_i+\omega)\ + e\sin\omega),$$ with $$K = \frac{m_p}{m_s+m_p}\frac{na\sin i}{\sqrt{1-e^2}}.$$ Being $V$the systematic velocity of the system, ...
3
votes
2answers
78 views

Night-Day Cycles in S-Type Planetary Systems

I am a writer and space enthusiast. For a story I am currently writing I would like to have a planet which orbits a star which resembles the sun, which in turn orbits another star. In this situation ...
3
votes
1answer
122 views

Mars is getting closer to Earth through its elliptical orbit becoming more eccentric. Do Earth and Mars keep getting closer? [closed]

A NASA Mars article says: Mars' orbit is more elliptical than Earth's, so the difference between perihelion and aphelion is greater. Over the past centuries, Mars' orbit has been getting more and ...
3
votes
1answer
235 views

For what parameter does the abbreviation MA stand for?

In the sentence: "We added a Keplerian model with P = 120.713 days, m = 14.629M⊕, e = 0.0448, ω = 251.36°, and MA=216.88° plus Gaussian noise with rms=5.9696 ms-1." P is the orbital period, ...
3
votes
2answers
181 views

Is this a potential planetary setup for the Alpha Centauri System?

I originally posted this on the World Building SE, but I was suggested to post it here for a better answer. I am attempting to create a [semi]plausible star system in Alpha Centauri for a series. The ...
3
votes
2answers
712 views

Does natural satellite(s) of a planet affects its orbital velocity around a star?

Please excuse me for a lay question. As we know, to calculate the orbital velocity, we take the mass of the orbiting body, the mass of the body being orbited and the distance between the two bodies ...
3
votes
2answers
52 views

What are the values of the Mean Anomalies of the planets in the Solar System?

I am trying to find a list of all the Mean Anomalies of the planets in the Solar System at the Epoch Jan 2000. I tried to Google it up but couldn't find any result. Can you please share the values or ...
3
votes
2answers
111 views

How to calculate center (not focus) of planetary orbit?

I'm developing a website showing the movement of Solar System planets according to the passage of time. I'm using this reference to calculate all the necessary orbital parameters. These are two images ...
3
votes
1answer
273 views

Easy interactive visualization of orbital elements

To get a grip on orbital elements, I'd like to play with a ready interactive visualization like in Universe Sandbox. E.g. drag the inclination slider and see immediately what happens to the satellite ...
3
votes
2answers
129 views

How was this interstellar fireball observed and its trajectory analyzed?

The short, interesting paper Discovery of a Meteor of Interstellar Origin describes a proposed discovery of a second interstellar object. This one hit the Earth, and was discovered not by telescope, ...
3
votes
1answer
343 views

How to calculate planetary position over vast time spans

Ignoring the turbulent beginnings of our solar system I wonder if there is a meaningful way to calculate the relative position of the planets of our solar system 100 million years into the future ...
3
votes
2answers
286 views

How to calculate the argument of perihelion for exoplanets with incomplete orbital elements?

I'm trying to simulate the Kepler-444 exoplanetary system using data from this website. The problem is that there is no argument of periapsis parameter for the Kepler-444 system, so while I think I'm ...
3
votes
1answer
973 views

Calculate the orbital phase when plotting the Radial Velocity data of a transitting exoplanet

I'm not quite sure how I find the orbital phase ($\phi$) of a transitting exoplanet. For example, I have this RV data in this article: First of all, I don't know how that phase or "cycles" is ...
3
votes
1answer
229 views

Given sunrise, noon, sunset, longitude and latitude can I calculate the "hight" or "ascension" of the sun?

I'm trying to make a simple app for my own use to be able to check which of my favorit restaurants have outdoor seating sun and for how long etc. Given the data in the title (sunrise, noon, sunset, ...
3
votes
1answer
558 views

Are ascending node of sun, the point of intersection of prime meridian and equator and center of earth all collinear?

I did a bit of googling but couldn't find the exact answer, so are the following 3 points collinear or not ? 1_center of earth 2_ascending(or descending) node of sun 3_point of intersection of ...